PROJECT ABSTRACT Prominent scholars have theorized that psychosocial moderation of genetic influences (referred to as gene-environment interactions; GxE) represents a fundamental etiologic component in child conduct problems (CP; aggressive and rule-breaking behaviors). Even so, only a handful of empirical studies have examined these processes to date. Though these seminal studies have provided provocative support for GxE in CP, additional work is needed to more fully flesh out their role. For example, though there is strong evidence within the animal literature that normal-range parenting serves as a potent moderator of genetic influences on offspring outcomes, most GxE research to date has focused on extreme environmental pathogens such as child maltreatment. Thus, although they are likely to be important, we know very little about the role of non-abusive, but still dysfunctional, parent- child relationships in moderating genetic influences on child CP. The role of protective relationships in suppressing genetic influences for child CP has also been largely overlooked, despite its oft- discussed prevention implications. Finally, few studies have controlled for gene-environment correlations (rGE), or non-random exposure to particular environmental experiences, a fundamental confound in GxE research. For example, if negative interpersonal relationships stem in part from genes common to CP, then the potentiation of genetic influences at high levels of environmental risk could be a reflection of rGE processes, rather than true GxE. The proposed research seeks to address these limitations, bringing together several unique elements to integrate the genetic and psychosocial mechanisms underlying child CP across multiple levels of analysis. The sample will consist of 500 community-based, same-sex twin pairs and their parent(s), a design that enables us to evaluate the moderating roles of both protective and risky parent-child relationships. Analyses will sequentially combine both quantitative and molecular genetic GxE approaches, as well as control for possible rGE, thereby overcoming most methodology-specific limitations and confounds. Our investigation thus combines state-of-the-art ideas and methods to examine GxE in CP, and accordingly, has the potential to significantly advance our understanding of the origins of child conduct problems.